Compensating electrode



March 1954 r w. MEIER 2,671,872

ICOMPENSATING ELECTRODE 7 Filed May 15 1952 FIG. I

WILBER L. MEIER INVENTOR.

ATTORNEY Patented Mar. 9, 1954 UNITED STATES PATENT OFFICE COMPENSATING ELECTRODE Wilber L. Meier, Chatham; N. J.

Application-May 15, 1952,, SeriaLNo. 287,908

Claims.

1 This. invention relates to a compensating elec trodev which is added to; vacuum electron. discharge devices such as triodes, pentodes, or other similar devices and to gas filled grid controlled tubes to compensat both for variable electrontubes a shift in the control characteristic results in a change in the grid breakdown or firing voltage.

Th need for compensating circuits for direct current amplifiers has been recognized for some time and many circuits have been devised and used to maintain the anode current constant while the cathode heater current changes in value. Some of the prior art circuits work well but all have one or more limitations and disadvantages. Some of the proposed circuits use a second tube, usually a diode, with heater elements connected in parallel with the amplifier tube to be compensated. The diode current is applied to the amplifier circuit in such a manner as to cancel the amplifier variations. Other proposed methods include voltage feed-back circuits through a diode to partly control the potential of the amplifier grid. All these systems require anextra tube and produce effective and true compensation only when the characteristics of the heaters and cathodes are the same in both tubes.

One of the objects ofthis invention is to provide an improved compensating electrode and regulating circuit which avoids one or more of th disadvantages and limitations of prior art arrangements.

Another object of the invention is to provide a compensating electrode arrangement which is contained in an amplifier or a grid controlled gas filled tube and dispenses with additional tubes.

Another object of the invention is to reduce 2, ing a compensating electrode with some parts shown in perspective.

Fig. 2 is a cross sectional view of the tube of. Fig-.1, taken along line 2-2- of that figure.

Fig. 3 is a schematic diagram of connections. showing how the compensating electrode is connected when used with a triode amplifier.

The present invention comprises the additionof a small electrode mounted beside the cathode in an amplifier tube. For best results the compensating. electrode may be a wir and shouldv be placed parallel to the cathode surface and atv a position where itis not too close to the grid. The compensating electrode is connected to the. cathode through a capacitor-resistor regulating circuit which permits the electrode to assumea potential which varies with the. cathode emission. Input signals to the amplifier stage are applied between the grid and the compensating. electrode.

Referring now to Figs. 1 and 2', an envelope. [0? encloses, the. component parts in a vacuum with. lead-in conductors II held by a seal l2. An insulating mica disk l3 holds the top portions. of the components in place. These components include an anode I4,v a grid l5, and a cathode it having. a heater element l'|. A compensating electrode I8 is mounted parallel to the cathode l6 and is positioned. about midway between the? cathode surface and one of the mounting rods to which the grid wires, are welded.

The circuit shown in Fig. 3 includes the usual anode. battery 20 which supplies current to the anode ['4 through an anode resistor 21. Output terminals 22 are provided for connection to a load circuit. Input terminals 23 are connected directlyto the. grid and the compensating electrode. In order to produce the proper potential onthe. compensating electrode, a resistor 24' and a capacitor 25 are connected in parallel between the compensating electrode and the cathode.

The operation of this circuitis as follows: When the. correct current is supplied to the cathodeheater and the cathode surface is emitting a steady and unvarying supply of electrons, a small percentage of the electrons strike the compensating electrode and cause a current toflow through. resistor 24' back to the cathode. This current produces a potential drop acrosstheresistor and the compensating electrode assumes a negative. potential, the value of which depends upon the resistance. element 24. The grid l5 assumes. the. samepotential because of the conductive connection through an input signal circuit 26. Now. let it be assumed that the. heater current. is changed: so. that the, electron emissionand the velocity of the emitted electrons is reducediasmalll amount. Such. an. action the usual form-ct vacuum triode causes. a reduction at the anode current. and. otherwise: changes the operating;

' 3 characteristics. In the above described tube and circuit, the reduced supply of electrons lowers the current through resistor 24 and, therefore, reduces the amount of negative potential applied to the compensating electrode and the grid. With a large enough value of resistance 24 the change of potential applied to the grid l5, almost exactly compensates for the drop in electron emission so that the anode current remains constant.

Capacitor 25 is connected across the terminals of resistor 24 to act as a storage device and to provide a low impedance path for alternating current signals between the lower terminal 23 and the cathode conductor.

The action of the compensating electrode in the case of the usual form of gas-filled grid-controlled tubes is similar to the above described action. A change of electron emission above or below a normal value causes the firing potential of the grid to vary. In the above described tube and circuit the reduced supply of electrons lowers the current through resistor 24 and reduces the negative potential applied to the grid by an amount which compensates for the drop in electron emission.

While there have been described and illustrated specific embodiments of the invention, it will be obvious that various changes and modifications may be made therein without departing from the field of the invention, which should be limited only by the scope of the appended claims.

What is claimed is:

1. A compensating arrangement for electron devices comprising; an electron discharge device containing an anode, a cathode, a grid, and a compensating electrode; a resistor connected between the compensating electrode and the cathode; and an input circuit connected to the grid and the compensating electrode.

2. A compensating arrangement for electron discharge devices comprising; an electron discharge device containin an anode, a cathode, a grid, and a compensating electrode positioned between the cathode and the grid; a resistor connected between the compensating electrode and the cathode; and an input circuit connected to the grid and the compensating electrode.

3. A- compensating arrangement for electron discharge devices comprising; an electron discharge device containing an anode, a cathode, a grid, and a compensating electrode positioned between the cathode and the grid; a regulating circuit which includes a resistor and a capacitor in parallel arrangement connected between the compensating electrode and the cathode; and an input circuit connected to the grid and the compensating electrode.

4. A compensating arrangement for electron discharge devices comprising; an electron discharge device containing an anode, a cathode, a grid, and a compensating electrode positioned between the cathode and the grid; a regulating circuit which includes a resistor and a capacitor in parallel arrangement connected between the compensating electrode and the cathode, said resistor having a value sufncient to apply a negative potential to the grid; and an input circuit con nected to the grid and the compensating electrade.

5. A compensating arrangement for high vacuum electron discharge devices for maintaining constant anode-cathode current comprising; an electron discharge device containing an anode, a cathode, a grid, and a compensating electrode positioned between the cathode and the grid; at

regulating circuit which includes a resistor and a capacitor in parallel arrangement connected between the compensating electrode and the cathode, said resistor having a value sufiicient to apply a negative potential to the grid; and an input circuit connected to the grid and the compensating electrode.

6. A compensating arrangement for gas filled electron discharge devices for maintaining constant grid breakdown voltage comprising; an electron discharge device containing an anode, a cathode, a grid, and a compensating electrode positioned between the cathode and the grid; a regulating circuit which includes a resistor and a capacitor in parallel arrangement connected between the compensating electrode and the cathode, said resistor having a value sufilcient to apply a negative potential to the grid; and an input circuit connected to the grid and the compensatin electrode.

7. A compensating arrangement for electron discharge for maintaining constant anode-cathode current comprising; an electron discharge device containing an anode, a cathode, a grid, and a compensating electrode positioned between the cathode and the grid; a regulating circuit which includes a resistor and a capacitor in parallel arrangement connected between th compensating electrode and the cathode, said resistor having a value sufficient to apply a negative potential to the grid, the value of said potential depending upon the electron emission and the velocity of the emitted electrons from the cathode; and an input circuit connected to the grid and the compensating electrode.

8. An electron discharge device in combination with a circuit which maintains a constant anodecathode current, said circuit including; an evacuated envelope containing an anode, a cathode, a grid, and a compensating electrode positioned between the cathode and the grid; an input circuit connected to the grid and the compensating electrode; an an impedance containing resistance connected between the cathode and the compensating electrode.

9. An electron discharge device in combination with a circuit which maintains a constant anodecathode current, said circuit including; an evacuated envelope containing an anode, a cathode, one or more grids, and a compensating electrode positioned adjacent to the cathode; an input circuit connected to one of the grids and the compensating electrode; and an impedance containing resistance connected between the cathode and the compensating electrode.

10. An electron discharge device in combination with a circuit which maintains a constant anode-cathode current, said circuit including; an evacuated envelope containing an anode, a cathode, a plurality of grids, and a, compensating electrode positioned adjacent to the cathode; said compensating electrode comprising one or more wires mounted parallel to the cathode and having a surface area which is less than the surface area of the adjacent grid; a signal input circuit connected to one of the grids and the compensating electrode; and an impedance containing resistance connected between the cathode and the compensating electrode.

WILBER L. MEIER.

Name Date Loper July 18, 1950 Number 

